1. Field of the Invention
The present invention relates to a Vacuum Processing Equipment and a vacuum processing method for improved vacuum pumping performance.
2. Detailed Description of Related Art
A structure of a prior art vacuum processing equipment is illustrated schematically by referring to the typical sputtering equipment shown in FIG. 1. The equipment has a vacuum chamber (or sputtering chamber) 10, in which is provided a cathode 12 capable of including a target, a shutter 14 capable of being opened and closed, a holder 16 for holding a wafer, heaters 18 and 20 for baking and cooling down 22 and 24. The chamber 10 is also provided with a wafer conveying system 26 for in-line processing and a gas supplying system 28. The chamber 10 is further provided with a main pumping mechanism for vacuum pumping it. The main pumping mechanism is a complicated mechanism including a rough vacuum pump 30 and a main pump 32, for example, a cryogenic and the like.
Reference number 34 is a wafer. The chamber 10 is usually kept in a vacuum. In this state the wafer can be put on the holder 16 in the chamber 10 and also taken out of the same by the wafer conveying system 26. Reference number 36 is a rough pumping valve 36. At reference number 38 is a main valve. The above various constituent elements may have well-known specific structures, thus the matter of detail are not described.
The chamber 10 is pumped down with the main vacuum pumping mechanism of the sputtering equipment as follows.
First of all, the chamber 10 is preliminarily evacuated with the rough vacuum pump 30. After completing the rough evacuation, the rough vacuum pump 30 is switched over to the main pump 32 to pump down the chamber 10 to as high a vacuum as about 10.sup.-7 Torr. Usually during evacuating, the chamber 10 is baked by operating the heaters 20 and 18 in suitable timings.
However, as described above, the chamber 10 accommodates various constitute elements, and therefore its actual inner surface area is very large. Besides, since it extensively uses elastomer gaskets (mainly Byton O-ring), sufficient baking can not be obtained. Therefore the attainable ultimate vacuum is as low as about 10.sup.-7 Torr. A high vacuum in the order of 10.sup.-8 is obtainable by performing long time baking and target cleaning. Heretofore, however, a couple of days were necessary to reach 7.times.10.sup.-8 Torr. This fact is applicable not only to the sputtering apparatus but also the other apparatuses such as dry etching apparatus as well.
It is well known in the prior art that the vacuum degree is still low, and it takes long time to reach the desired pressure. Thus, there arises a problem in that it is impossible to improve the throughput.
The inventors of this application, accordingly, have conducted research and investigations for a purpose of improving the pumping performance (i.e., attainable ultimate vacuum degree and pumping time).
They have reached the conclusion that the evacuation of residual atmospheric main gases in the chamber, excluding the introduced gas under the ultimate pressure, are H.sub.2, H.sub.2 O, N.sub.2 +CO, CO.sub.2, etc., as shown in FIG. 3. The predominant gases among them is H.sub.2 O (water component). Therefore, in the equipment of the prior art, water (H.sub.2 O) is present as a main component of the residual gas due to the equipment having complicated construction and a lack of baking. This water component determines a limit on the pumping performance such as attainable ultimate pressure and pumping time. As a result, the pumping performance can be improved by trapping at least the water component among the residual gas components.